An image forming apparatus, such as a printer, a multi function device, a copy machine, or a facsimile machine, performs printing on a recording sheet by an electrophotographic process. In the electrophotographic process, a charger generates corona discharge to form a surface potential on a photosensitive member, and an electrostatic latent image is formed on the surface of the photosensitive member by an exposure device. Thereafter, toner is attached to the photosensitive member to visualize the electrostatic latent image, and toner on the photosensitive member is transferred and fixed to the recording sheet. After toner is transferred to the recording sheet, non-transferred toner remaining on the photosensitive member is cleaned, and the residual surface potential is eliminated by a static eliminator.
While the image forming apparatus repeats printing, toner or sheet dust is stuck to a wire of the charger or the static eliminator, and the wire is thickened. The thickened wire becomes closer to the photosensitive member. This thickened wire or a crack occurs in the distribution of a toner attached to the photosensitive member might causes arc discharge. In the image forming apparatus, if arc discharge is generated, corona discharge which is normal discharge is obstructed. For this reason, black lines and streaks appear, and accordingly printing performance is seriously deteriorated. In addition, the recording sheet or toner is wasted.
Accordingly, there has been suggested a technique to detects abnormality in the charger or the static eliminator. For example, JP-A-2007-178595 describes an image forming apparatus including: four photosensitive members to which toner of yellow, magenta, cyan and black are supplied, respectively; chargers and static eliminators which are opposed to the four photosensitive members, respectively and to which power is supplied from a high-voltage power supply unit; and a discharge detection circuit which is connected to each charger or each static eliminator and detects abnormal discharge of the charger or the static eliminator. According to the image forming apparatus described in JP-A-2007-178595, a user can be asked to clean the charger or the static eliminator in which abnormal discharge is detected. As a result, deterioration in printing performance and wasteful recording sheet or toner can be suppressed.
However, related-art image forming apparatuses can detect abnormal discharge of the charger or the static eliminator but do not confirm whether the user actually cleans the charger or the static eliminator. Therefore, if the user executes re-printing before the charger or the static eliminator is cleaned, abnormal discharge is generated again in the image forming apparatus. In the image forming apparatus, the charger or the static eliminator may be broken down if such abnormal discharge occurs repeatedly.